It is known to equip a motor vehicle with a system including sensors to detect potential obstacles behind or potentially crossing behind the subject vehicle. When the subject vehicle is driving in reverse, e.g. backing out of a parking space, the known systems are intended to provide a warning to the driver of the subject vehicle if there is an obstacle behind or potentially crossing behind the subject vehicle. The known systems in modern series production motor vehicles function on the basis of a warning zone defined behind the subject vehicle. In this regard, a limited lateral or rearward zone is defined around and behind the subject vehicle. In a typical parking situation, for example when the subject vehicle is backing out of a parking space, the system will then produce a warning to the driver when an obstacle object such as a car or a motorcycle has entered completely or at least partially into this warning zone. However, in many situations, such known systems will not generate a warning early enough. For example, in the case of an obstacle vehicle that is not yet in the warning zone but is approaching this zone from the side at a high speed, such a known system that is only triggered when the obstacle vehicle reaches the warning zone, would generate the warning too late for the driver to be able to react adequately to the situation.
Another problem with known systems is that they do not take into account the approach angle of a potential obstacle vehicle that is approaching the warning zone from the side at an oblique or non-perpendicular angle. Therefore, the known systems cannot accurately predict whether a collision or time-critical intersection of the subject vehicle or its warning zone with the trajectory of the potential obstacle vehicle will occur, especially when the obstacle vehicle is approaching at an oblique angle relative to the longitudinal axis of the subject vehicle. Thus, the known systems are especially inadequate in typical angled parking situations, in which cars are parked at an oblique non-perpendicular angle relative to a roadway or a parking area lane extending behind the cars.